[PATCH] pretest pte_young and pte_dirty

[Hugh Dickins]

Test for pte_young before going to the costlier atomic test_and_clear,
as asm-generic does.  Test for pte_dirty before going to the costlier
atomic test_and_clear, as asm-generic does (I said before that I would
not do so for pte_dirty, but was missing the point: there is nothing
atomic about deciding to do nothing).  But I've not touched the rather
different ppc and ppc64.

Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>

 include/asm-i386/pgtable.h   |   16 ++++++++++++++--
 include/asm-ia64/pgtable.h   |    4 ++++
 include/asm-parisc/pgtable.h |    4 ++++
 include/asm-x86_64/pgtable.h |   17 +++++++++++++++--
 4 files changed, 37 insertions(+), 4 deletions(-)

--- 2.6.7-rc2/include/asm-i386/pgtable.h	2004-05-30 11:36:30.000000000 +0100
+++ linux/include/asm-i386/pgtable.h	2004-06-02 16:32:40.032214544 +0100
@@ -220,8 +220,20 @@ static inline pte_t pte_mkdirty(pte_t pt
 static inline pte_t pte_mkyoung(pte_t pte)	{ (pte).pte_low |= _PAGE_ACCESSED; return pte; }
 static inline pte_t pte_mkwrite(pte_t pte)	{ (pte).pte_low |= _PAGE_RW; return pte; }
 
-static inline  int ptep_test_and_clear_dirty(pte_t *ptep)	{ return test_and_clear_bit(_PAGE_BIT_DIRTY, &ptep->pte_low); }
-static inline  int ptep_test_and_clear_young(pte_t *ptep)	{ return test_and_clear_bit(_PAGE_BIT_ACCESSED, &ptep->pte_low); }
+static inline int ptep_test_and_clear_dirty(pte_t *ptep)
+{
+	if (!pte_dirty(*ptep))
+		return 0;
+	return test_and_clear_bit(_PAGE_BIT_DIRTY, &ptep->pte_low);
+}
+
+static inline int ptep_test_and_clear_young(pte_t *ptep)
+{
+	if (!pte_young(*ptep))
+		return 0;
+	return test_and_clear_bit(_PAGE_BIT_ACCESSED, &ptep->pte_low);
+}
+
 static inline void ptep_set_wrprotect(pte_t *ptep)		{ clear_bit(_PAGE_BIT_RW, &ptep->pte_low); }
 static inline void ptep_mkdirty(pte_t *ptep)			{ set_bit(_PAGE_BIT_DIRTY, &ptep->pte_low); }
 
--- 2.6.7-rc2/include/asm-ia64/pgtable.h	2004-05-30 11:36:31.000000000 +0100
+++ linux/include/asm-ia64/pgtable.h	2004-06-02 16:32:40.034214240 +0100
@@ -346,6 +346,8 @@ static inline int
 ptep_test_and_clear_young (pte_t *ptep)
 {
 #ifdef CONFIG_SMP
+	if (!pte_young(*ptep))
+		return 0;
 	return test_and_clear_bit(_PAGE_A_BIT, ptep);
 #else
 	pte_t pte = *ptep;
@@ -360,6 +362,8 @@ static inline int
 ptep_test_and_clear_dirty (pte_t *ptep)
 {
 #ifdef CONFIG_SMP
+	if (!pte_dirty(*ptep))
+		return 0;
 	return test_and_clear_bit(_PAGE_D_BIT, ptep);
 #else
 	pte_t pte = *ptep;
--- 2.6.7-rc2/include/asm-parisc/pgtable.h	2004-05-30 11:36:33.000000000 +0100
+++ linux/include/asm-parisc/pgtable.h	2004-06-02 16:32:40.035214088 +0100
@@ -417,6 +417,8 @@ extern void update_mmu_cache(struct vm_a
 static inline int ptep_test_and_clear_young(pte_t *ptep)
 {
 #ifdef CONFIG_SMP
+	if (!pte_young(*ptep))
+		return 0;
 	return test_and_clear_bit(xlate_pabit(_PAGE_ACCESSED_BIT), ptep);
 #else
 	pte_t pte = *ptep;
@@ -430,6 +432,8 @@ static inline int ptep_test_and_clear_yo
 static inline int ptep_test_and_clear_dirty(pte_t *ptep)
 {
 #ifdef CONFIG_SMP
+	if (!pte_dirty(*ptep))
+		return 0;
 	return test_and_clear_bit(xlate_pabit(_PAGE_DIRTY_BIT), ptep);
 #else
 	pte_t pte = *ptep;
--- 2.6.7-rc2/include/asm-x86_64/pgtable.h	2004-05-30 11:36:35.000000000 +0100
+++ linux/include/asm-x86_64/pgtable.h	2004-06-02 16:32:40.036213936 +0100
@@ -262,8 +262,21 @@ extern inline pte_t pte_mkexec(pte_t pte
 extern inline pte_t pte_mkdirty(pte_t pte)	{ set_pte(&pte, __pte(pte_val(pte) | _PAGE_DIRTY)); return pte; }
 extern inline pte_t pte_mkyoung(pte_t pte)	{ set_pte(&pte, __pte(pte_val(pte) | _PAGE_ACCESSED)); return pte; }
 extern inline pte_t pte_mkwrite(pte_t pte)	{ set_pte(&pte, __pte(pte_val(pte) | _PAGE_RW)); return pte; }
-static inline  int ptep_test_and_clear_dirty(pte_t *ptep)	{ return test_and_clear_bit(_PAGE_BIT_DIRTY, ptep); }
-static inline  int ptep_test_and_clear_young(pte_t *ptep)	{ return test_and_clear_bit(_PAGE_BIT_ACCESSED, ptep); }
+
+static inline int ptep_test_and_clear_dirty(pte_t *ptep)
+{
+	if (!pte_dirty(*ptep))
+		return 0;
+	return test_and_clear_bit(_PAGE_BIT_DIRTY, ptep);
+}
+
+static inline int ptep_test_and_clear_young(pte_t *ptep)
+{
+	if (!pte_young(*ptep))
+		return 0;
+	return test_and_clear_bit(_PAGE_BIT_ACCESSED, ptep);
+}
+
 static inline void ptep_set_wrprotect(pte_t *ptep)		{ clear_bit(_PAGE_BIT_RW, ptep); }
 static inline void ptep_mkdirty(pte_t *ptep)			{ set_bit(_PAGE_BIT_DIRTY, ptep); }
 

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